This invention relates generally to power plants, and, more specifically to hybrid power plants with integrated fuel cells, where the controlled injection of exhaust air from the fuel cell is used to burn the spent fuel from the fuel cells.
In certain hybrid power generation systems, fuel cells have been integrated with conventional gas turbines for increased power generation capacity in electrical power plants. Known fuel cells, such as, for example, solid oxide fuel cells include a plurality of solid oxide fuel cells that react a gaseous fuel, such as reformed natural gas, with air to produce electrical power and a hot gas. The gas turbine compressor supplies the air for the fuel cells, which fuel cells operate at elevated pressure and produce hot gas for expansion in the turbine. Fuel cell exhaust air is combined with fuel cell exhaust fuel and the resulting heat release is converted to work in the turbine portion of the plant. Thus, electrical power is produced by both the solid oxide fuel cell generator and the turbine.
Solid-oxide fuel cells usually do not convert all of the fuel that is fed into the inlet of the fuel cells. Composition of the outlet stream from the fuel cells primarily includes carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), and water (H2O) along with the equilibrium species and inert species like N2. In the absence of means to burn the partly spent fuel, the heat content of these constituents is wasted, thereby reducing thermodynamic efficiency of the plant. Additionally, unburned hydrocarbons and carbon monoxide may also be undesirably emitted into the atmosphere when all the fuel components for the fuel cells are not completely converted.
Accordingly there is a need to develop a combustor or a burner that can efficiently convert the fuel components in the spent fuel stream from the fuel into useful work using the fuel cell exhaust air.